1. Technical Field
The embodiments herein generally relate to communication systems, and, more particularly, to layer coded orthogonal frequency division multiplexing (OFDM) communication systems.
2. Description of the Related Art
Concatenated coding schemes have been widely used in many OFDM communication systems. A concatenated coding scheme used in Integrated Services Digital Broadcasting—Terrestrial (ISDB-T), Digital Video Broadcasting—Terrestrial/Handheld (DVB-T/H), and Terrestrial—Digital Multimedia Broadcasting (T-DMB) has the convolutional code as the inner code and Reed-Solomon code as the outer code. Another concatenated decoding scheme uses the classic Viterbi decoder to decode the convolutional code. The Viterbi decoder outputs hard decisions, and the hard decisions are de-interleaved and passed on to a classic hard-decision RS decoder.
Turbo decoding for concatenated coding schemes involves iterative decoding and information exchanging between the inner decoder and the outer decoder. In turbo coding, a soft decision RS decoder and soft output convolutional code decoder is needed. The soft output convolutional code decoder can be a soft-output Viterbi decoder (SOVA) or a Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm based MAP decoder. Both types of decoders are generally very complicated compared to the classical hard decision Viterbi decoder. A classical Viterbi decoder typically cannot take extrinsic information, and hence typically cannot be used in the iterative or turbo decoding schemes. Compared with the classic hard decision RS decoder, the soft decision RS decoder is also very complicated. In addition, the de-interleaver and interleaver may have to store soft decisions from the soft output convolutional code decoder and the soft decision RS decoder, and the memory to store the de-interleaved and interleaved soft decisions could be substantial.